A cobalt monatomic-loaded polyphosphazene / MXene self-supporting electrode and a preparation method and application thereof

Abstract

This invention discloses a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, its preparation method, and its application, belonging to the field of seawater uranium extraction technology. Ti3AlC2 powder is etched in an HCl-LiF mixed solution and then ultrasonically exfoliated to obtain Ti3C2T. x Nanosheet suspension; simultaneously, hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, and cobalt salt were dissolved in a solvent, and triethylamine was added. A condensation reaction was then carried out under ultrasonication to obtain Co-PZS; then Ti3C2T x After the nanosheet suspension is uniformly mixed with Co-PZS and carbon fiber fabric, it is transferred to a hydrothermal reactor for hydrothermal reaction. The resulting hydrothermal reaction product is then dried and calcined to obtain a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms. This electrode is used for the electrochemical adsorption of uranyl ions in the solution system and exhibits excellent comprehensive uranium extraction performance, with advantages such as high capacity, fast rate, strong selectivity, and good stability, meeting the application requirements of seawater uranium extraction.

Description

Technical Field

[0001] This invention relates to an electrode, particularly to a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, and also to a method for preparing the electrode and its application in uranyl ions in an electrochemical adsorption solution system, belonging to the field of seawater uranium extraction technology. Background Technology

[0002] Uranium is a crucial resource for the sustainable development of nuclear energy. Although terrestrial uranium reserves are limited, ocean uranium reserves far exceed those on land, possessing a significant order-of-magnitude advantage. Therefore, the efficient extraction of uranium from seawater has become an important direction for ensuring future uranium resource supply. Currently, commonly used methods include adsorption, ion exchange, membrane separation, photocatalysis, and electrochemical methods. Among these, electrochemical methods have attracted increasing attention due to their superior interface control capabilities and enhanced kinetic performance. Particularly noteworthy is the significant potential of the square wave exchange method. The periodic switching of the square wave voltage can dynamically regulate the electric field at the electrode interface, accelerating the extraction of uranyl ions (UO2). 2+ This approach improves uranium selectivity by migrating ions, enhancing mass transfer efficiency, and by precisely controlling the potential window, suppressing the co-deposition of competing ions. Despite the promising outlook of this strategy, there is still room for improvement in the electrocatalytic performance of the electrode materials.

[0003] In recent years, single-atom catalysts (SACs) have attracted much attention due to their ability to convert every metal atom into an active site and maximize atom utilization. They not only exhibit excellent catalytic performance with extremely low metal loadings but also significantly reduce material costs. However, isolated metal atoms have high surface energy and are prone to aggregation, requiring suitable supports for stabilization. Furthermore, the interaction and coordination environment between the metal atoms and neighboring non-metal atoms on the support directly determine the catalytic activity, selectivity, and metal loading of SACs. Constructing strong metal-support interactions (SMSIs) is the core strategy for synthesizing stable SACs.

[0004] Since the discovery of graphene, two-dimensional materials have attracted much attention in the field of materials science due to their unique morphology, high specific surface area, abundant coordination unsaturated sites, intrinsic defects, and tunable electronic structure. MXenes, as a novel class of two-dimensional materials (including metal carbides, nitrides, and carbonitrides), possess not only the common advantages of the aforementioned two-dimensional materials but also tunable surface chemical properties, excellent conductivity, high hydrophilicity, and good mechanical properties, showing broad application prospects in the field of electrochemistry. The defects naturally formed during the preparation of MXenes (such as vacancies and edge defects) and the abundant terminal functional groups (-OH, -O, -F, etc.) on the surface provide rich anchoring sites for metal single atoms. Stable loading of metal atoms can be achieved through strong covalent bonds or coordination interactions, effectively preventing their migration and aggregation, thereby constructing uniformly distributed and structurally well-defined active centers at the atomic level. Simultaneously, the high conductivity of the MXene matrix provides efficient electron transport pathways for single-atom active sites, accelerating charge transfer at the electrochemical reaction interface and promoting the reduction and deposition kinetics of uranyl ions, thus significantly improving the extraction rate and efficiency of uranium. Furthermore, the electronic regulation effect between the single-atom center and the functional groups on the MXenes surface can optimize the binding ability of uranyl ions, enhance the selective recognition and adsorption of uranium in complex seawater compositions, effectively suppress interference from other ions, and thus improve the purity of uranium extraction.

[0005] However, MXene nanosheets are prone to stacking during preparation and processing, and exhibit poor stability in electrochemical environments, leading to reduced interlayer distance and insufficient exposure of active sites, thus affecting ion transport efficiency and overall electrochemical performance. For example, Chinese patent application (CN119349720A) discloses a flow electrode with a metallo-oxime-functionalized MXene / CoZn-MOF heterostructure, its preparation method, and its application in the efficient adsorption of uranium in wastewater. By constructing a heterostructure of MXene and CoZn-MOF, it utilizes the high specific surface area and selective adsorption capacity of MOF, combined with the conductivity and flexibility of MXene, to a certain extent suppressing the stacking phenomenon of MXene nanosheets and improving charge transport and electrode performance. However, this method has a complex preparation process and relatively limited functional group types. The introduction of N, P, and S-doped polyphosphazene-derived carbon materials can effectively improve the stability of MXenes. Firstly, high-temperature carbonization of polyphosphazene forms a uniform and dense carbonaceous coating layer on the MXenes surface. This coating layer effectively blocks the contact between MXenes and dissolved oxygen and free radicals in water, significantly inhibiting the spontaneous oxidation and structural degradation of MXene sheets, thereby extending the material's lifespan in electrochemical environments. Secondly, this carbon layer acts as a spacer to prevent the recombination and aggregation of MXenes nanosheets, maintaining their open layered structure and high specific surface area, which is beneficial for the diffusion and contact of uranyl ions. Furthermore, the abundant PO and CN active sites in polyphosphazene can form strong chemical bonds with uranyl ions, thereby improving the adsorption capacity and selectivity for uranyl ions. For example, Chinese patent application (CN120247026A) discloses an MXene@PZSC gel-structured membrane electrode, its preparation method, and its application. This electrode utilizes a conductive polyphosphazene-derived carbon (PZSC) framework to immobilize MXene nanosheets, exhibiting good stability and effectively expanding the interlayer spacing of MXene to prevent stacking. It also possesses a fixed pore structure, further opening active sites, and can be used for the electrochemical separation of uranyl ions, achieving a maximum removal capacity of 3375.44 mg / g. However, this electrode mainly relies on the surface functional groups of MXene nanosheets and the porous structure of polyphosphazene-derived carbon to adsorb uranyl ions. Although it has a high specific surface area and good conductivity, the types and number of active sites may be relatively limited. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a self-supporting polyphosphazene / MXene electrode loaded with cobalt single atoms. This electrode uses a three-dimensional carbon felt as a carrier for the polyphosphazene / MXene active layer, imparting good conductivity to the active layer and ensuring sufficient solution penetration and efficient ion diffusion. Simultaneously, Co single-atom active sites are constructed on the polyphosphazene / MXene active layer, combined with binding sites rich in N, P, S, and other heteroatoms from polyphosphazene-derived carbon, creating a physicochemically synergistic uranium capture mechanism. This results in advantages such as electrode structural stability, high conductivity, high uranium extraction capability, and good selectivity.

[0007] The second objective of this invention is to provide a method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, which has the advantages of simple operation, low cost and controllable conditions.

[0008] The third objective of this invention is to provide an application of a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, which is used for the electrochemical adsorption of uranyl ions in a solution system. It exhibits excellent comprehensive uranium extraction performance, with advantages such as high capacity, fast rate, strong selectivity, and good stability, thus meeting the application requirements for seawater uranium extraction.

[0009] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, which includes the following steps:

[0010] 1) Ti3AlC2 powder was etched in an HCl-LiF mixed solution and then ultrasonically exfoliated to obtain Ti3C2T x Nanosheet suspension;

[0011] 2) After dissolving hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone and cobalt salt in a solvent, triethylamine was added, and a polycondensation reaction was carried out under ultrasonication to obtain Co-PZS;

[0012] 3) Ti3C2T x After the nanosheet suspension is mixed evenly with Co-PZS and carbon fiber fabric, it is transferred to a hydrothermal reactor for hydrothermal reaction. The resulting hydrothermal reaction product is then dried and calcined to obtain a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms.

[0013] The present invention provides a method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms. On the one hand, it utilizes the coordination effect of PZS to stabilize the binding of cobalt ions, and on the other hand, it utilizes PZS to introduce cobalt ions into Ti3C2T. xThe nanosheets allow for uniform dispersion and stable loading of cobalt ions within polyphosphazene / Mxene. During high-temperature processing, cobalt single atoms are generated in situ, and these atoms are effectively anchored to their designated sites, ensuring stable loading and preventing migration and aggregation. This results in the construction of uniformly distributed and structurally defined active centers at the atomic level. Secondly, PZS is used to assemble Ti3C2T. x Nanosheets, through electrostatic interactions between the two, achieve Ti3C2T x The disordered stacking of nanosheets, with PZS filling Ti3C2T x The interlayer of nanosheets can expand Ti3C2T x The spacing between the nanosheets prevents Ti3C2T x The ordered stacking of nanosheets simultaneously constructs a unique three-dimensional porous structure that exposes Ti3C2T. x The nanosheets have more adsorption active sites; thirdly, polyphosphazene / MXene is grown in situ on a three-dimensional carbon felt using a hydrothermal method, allowing the polyphosphazene / MXene active layer to be directly chemically bonded to the three-dimensional carbon felt framework, constructing a seamless conductive network and eliminating the negative impact of insulating binders, while the three-dimensional porous carbon felt ensures sufficient electrolyte penetration and efficient ion diffusion; fourthly, through Ti3C2T x By constructing Co single-atom active adsorption sites on nanosheets, and combining these with adsorption sites constructed from heteroatoms such as N, P, and S abundant in polyphosphazene-derived carbon, a physicochemically synergistic uranium capture mechanism is created. This achieves highly efficient initial capture followed by rapid conversion of uranyl ions, exhibiting high selectivity even in complex seawater environments. In summary, the cobalt single-atom-loaded polyphosphazene / MXene self-supporting electrode prepared in this invention demonstrates excellent comprehensive uranium extraction performance: high capacity, fast rate, good selectivity, and strong stability.

[0014] As a preferred embodiment, the concentration of LiF in the HCl-LiF mixed solution is 60~100 mg / mL, and the concentration of HCl is not less than 8 mol / L. More preferably, the HCl concentration is 8~10 mol / L.

[0015] As a preferred embodiment, the ratio of the Ti3AlC2 powder to the HCl-LiF mixed solution is measured according to a mass ratio of Ti3AlC2 to LiF of 1:(1.5~2.0).

[0016] As a preferred embodiment, the etching conditions are: stirring reaction at 35~45℃ for 30~60h.

[0017] As a preferred embodiment, the molar ratio of hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, and cobalt salt is in the range of (15~25):(5~15):1. If the proportion of hexachlorocyclotriphosphazene is too low, insufficient cross-linking of the polyphosphazene network may occur, affecting its structural stability and mechanical properties. If the proportion of hexachlorocyclotriphosphazene is too high, the polyphosphazene network may become too dense, reducing porosity and specific surface area, thereby decreasing the adsorption performance for uranyl ions. If the proportion of cobalt salt is too low, insufficient loading of cobalt single atoms may occur, thereby reducing the electrode's adsorption and conversion capacity for uranyl ions. If the proportion of cobalt salt is too high, the cobalt single atoms may aggregate, forming larger cobalt particles, thus losing the high activity characteristics of single atoms.

[0018] As a preferred embodiment, the conditions for the polycondensation reaction are: ultrasonic power of 150~210W, frequency of 35~45Hz, temperature of 25~50℃, and time of 0.5~2.0h. The polycondensation reaction is carried out under ultrasonic treatment, which not only promotes the polymerization process but also facilitates the acquisition of uniform microspheres of PZS. These microspheres of PZS can effectively expand the interlayer structure of MXene, prevent stacking, and release a larger specific surface area and active sites. Simultaneously, ultrasonic treatment further promotes the uniform dispersion and loading of cobalt ions.

[0019] As a preferred embodiment, the Ti3C2T x The mass ratio of the nanosheet suspension to the Co-PZS is (5~15):1; if Ti3C2T x If the proportion of nanosheets is too high, PZS will be difficult to transfer to Ti3C2T. x The complete filling of the interlayer spaces of nanosheets will cause some Ti3C2T x The ordered stacking of nanosheets cannot fully utilize Ti3C2T x The layered structure and high specific surface area of ​​nanosheets reduce the adsorption capacity of the electrode. If Ti3C2T x If the proportion of nanosheets is too low, there will be fewer exposed active sites, resulting in poor electrode adsorption performance.

[0020] As a preferred embodiment, the Ti3C2T x Ti3C2T in nanosheet suspension x The concentration of nanosheets is 3~7 mg / mL.

[0021] As a preferred embodiment, the hydrothermal reaction is carried out at a temperature of 100-140°C for 3-7 hours. If the hydrothermal reaction temperature is too low, the reaction rate may be slow. xIncomplete assembly of nanosheets and Co-PZS on the surface of carbon fiber fabric may lead to insufficient conductivity and adsorption properties of the material. Excessively high hydrothermal reaction temperatures may cause structural damage or partial decomposition, affecting its structure and specific surface area, and reducing the material's adsorption performance. Under optimized hydrothermal reaction conditions, the adsorption of Ti3C2T can be promoted. x Nanosheets and Co-PZS are assembled in situ on the surface of carbon felt and uniformly loaded on the surface of carbon felt.

[0022] As a preferred embodiment, the calcination conditions are: calcination at 400-500℃ for 1-3 hours under a protective atmosphere. If the calcination time is too short or the temperature is too low, the carbonization process will be incomplete, resulting in a weak carbon skeleton structure that affects the conductivity and stability of the electrode material. If the calcination time is too long or the temperature is too high, it may lead to over-sintering of the carbon skeleton, causing the carbon skeleton structure to collapse, reducing porosity, and affecting the material's adsorption performance. Under the preferred conditions, high-temperature calcination transforms PZS into a hard carbon skeleton that is in situ bonded to the carbon felt surface, forming a bondless integral structure. This significantly improves the material's conductivity and structural stability. Simultaneously, the high temperature enables the in-situ reduction of cobalt ions to form Co single atoms, thereby enhancing the adsorption performance of the Ti3C2T electrode. x The nanosheets contain a large number of Co single-atom active adsorption sites, which, together with the adsorption sites constructed by the N, P, S and other heteroatoms in the polyphosphazene-derived carbon, and the porous carbon framework formed by the microsphere PZS, form a multi-synergistic adsorption mechanism for uranyl ions, which greatly improves its adsorption activity.

[0023] The carbon fiber fabric of this invention is pretreated by ultrasonically cleaning three times sequentially with 0.1 mol / L HNO3 solution, anhydrous ethanol, and deionized water to remove surface contaminants. The carbon felt has a size of 1 × 1.5 cm. The carbon fiber fabric can be carbon cloth, carbon felt, etc.

[0024] The present invention also provides a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, which is obtained by the preparation method described above.

[0025] The present invention also provides an application of a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, which is used as the working electrode of a dual-electrode system for the electrochemical adsorption of uranyl ions in a solution system.

[0026] As a preferred embodiment, during the operation of the dual-electrode system, the operating voltage is -5 to 0V, the operating frequency is 300 to 500 Hz, and the duty cycle is 40 to 60%. As a preferred embodiment, the pH of the solution system is controlled within the range of 2 to 7. More preferably, the pH of the solution system is controlled within the range of 5 to 7.

[0027] The dual-electrode system of this invention employs a square-wave exchange electrochemical method.

[0028] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0029] (1) The method for preparing the polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms provided by the present invention uses an in-situ growth method to directly chemically bond the polyphosphazene / MXene active layer onto the three-dimensional carbon felt skeleton, thereby constructing a seamless conductive network, eliminating the negative impact of insulating binder, and ensuring sufficient penetration of electrolyte and efficient diffusion of ions in the three-dimensional porous carbon felt.

[0030] (2) The method for preparing the polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms provided by the present invention utilizes PZS to uniformly introduce cobalt ions into Ti3C2T x Between the nanosheet layers, thus in Ti3C2T x The nanosheets form a large number of Co single-atom active adsorption sites, which, together with the adsorption sites constructed by the N, P, S and other heteroatoms in the polyphosphazene-derived carbon, and the porous carbon skeleton formed by the microsphere PZS, form a multi-synergistic adsorption mechanism for uranyl ions, which greatly improves its adsorption activity and enhances its adsorption selectivity.

[0031] (3) The polyphosphazene / MXene self-supporting electrode with cobalt single atoms provided by this invention exhibits excellent comprehensive uranium extraction performance in uranyl ions in solution systems, with advantages such as high capacity, fast rate, good selectivity, and strong stability. For example, under a square wave voltage of -5~0V, the electrode achieves an ultra-high uranium extraction capacity of 4000 mg / g within 7 h, and has good resistance to interference from common metal ions (V(V), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ca(II), Mg(II), etc.). In natural seawater, a high-efficiency uranium extraction capacity of 2.89 mg / g / d is achieved, and the uranium extraction capacity can still be maintained above 85% after six consecutive adsorption-desorption cycles.

[0032] (4) The preparation method of the polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms of the present invention has the advantages of simple operation, low cost and controllable conditions. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the Co-MPC@CF electrode preparation process in Example 1.

[0034] Figure 2 The image shown is a HAADF-STEM image of Co-MPC in Example 1.

[0035] Figure 3The image shows the XRD pattern of Co-MPC in Example 1.

[0036] Figure 4 This is the k²-weighted EXAFS plot of the Fourier transform of Co-MPC in Example 1.

[0037] Figure 5 The graph shows the change in uranium extraction capacity over time for different electrodes in Example 1 and Comparative Examples 1 to 3.

[0038] Figure 6 The graph shows the change in uranium extraction capacity of the Co-MPC@CF electrode in Example 1 as a function of the applied square wave voltage.

[0039] Figure 7 This is a comparison diagram of the selective adsorption of different metal ions by the Co-MPC@CF electrode in Example 1.

[0040] Figure 8 This is a diagram showing the uranium extraction effect of the Co-MPC@CF electrode in Example 1 after six cycles of regeneration in uranium-spiked seawater.

[0041] Figure 9 This is a diagram showing the extraction effect of uranium in real seawater using the Co-MPC@CF electrode in Example 1.

[0042] Figure 10 In Example 4, different Ti3C2T x Comparison of electrochemical uranium extraction performance with electrodes prepared at the Co-PZS ratio.

[0043] Figure 11 This is a comparison of the electrochemical uranium extraction performance of electrodes prepared at different hydrothermal temperatures in Example 5. Detailed Implementation

[0044] The following specific embodiments are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0045] Unless otherwise specified, the methods and raw materials used in the following examples are conventional and commercially available. Specific experimental conditions not specified will be performed in accordance with conventional methods or conditions recommended by the manufacturer.

[0046] Example 1

[0047] 1) Dissolve 3.2 g LiF in 40 mL of 9 mol / L HCl solution and react for 15 min at 40 °C and 200 rpm with stirring. Then add 2 g Ti3AlC2 powder and continue stirring under the same conditions for 48 h. After the reaction, transfer the resulting black viscous suspension to a centrifuge tube and wash three times with 2 mol / L HCl solution at 5000 rpm to remove impurities. Then wash with deionized water at 5000 rpm until the supernatant pH=6. Next, place it in an ice-water bath for ultrasonic exfoliation for 1 h (manually shaken every 10 min during this process). After ultrasonication, centrifuge at 3500 rpm for 30 min and collect the Ti3C2-rich Ti3AlC2T. x The supernatant of the nanosheets. For ease of subsequent use, the suspension was diluted with deionized water to 5 mg / mL and stored at 4°C under nitrogen protection.

[0048] 2) Place 100 mL of acetonitrile in a beaker, and under ultrasonic assistance (190 W, 40 kHz), add 0.4868 g of hexachlorocyclotriphosphazene (HCCP), 0.2628 g of 4,4'-dihydroxydiphenyl sulfone (BPS), and 0.025 g of cobalt chloride hexahydrate (CoCl2·6H2O) sequentially until completely dissolved. Continue ultrasonication for 10 min, then add 3.00 mL of triethylamine (TEA) to initiate the reaction, and sonicate for 1 h. After the reaction is complete, wash the resulting precipitate three times each with deionized water and anhydrous ethanol (10000 rpm), and then vacuum dry at 60 °C for 12 h to obtain Co-PZS.

[0049] 3) Cut the graphite fiber felt into strips of 1×1.5cm, and ultrasonically clean it three times successively with 0.1mol / L HNO3 solution, anhydrous ethanol, and deionized water to remove surface contaminants. Dry the cleaned carbon felt for later use. Take 12mL of 5mg / mL Ti3C2T... x The suspension and 0.60 g of Co-PZS powder were placed in a container with 10 mL of deionized water and a piece of pretreated graphite fiber felt, and stirred for 1 h. The mixture (including the impregnated graphite fiber felt) was then transferred to a PTFE-lined hydrothermal reactor and reacted at 120 °C for 5 h. After the reaction, the graphite fiber felt was removed, rinsed with deionized water, and vacuum-dried at 60 °C for 12 h. The dried graphite fiber felt was then placed in a tube furnace and heated to 450 °C at a rate of 5 °C / min under a N2 atmosphere and held for 2 h. After cooling, the polyphosphazene / MXene self-supported electrode (Co-MPC@CF) loaded with cobalt single atoms was obtained.

[0050] Figure 1 This is a schematic diagram of the Co-MPC@CF preparation process in Example 1.

[0051] The Co-MPC active material on the surface of the graphite fiber felt was exfoliated and characterized:

[0052] Figure 2 The image shows a HAADF-STEM image of Co-MPC. As can be seen from the image, there are many isolated bright spots of atomic size (highlighted by yellow dashed circles), indicating that Co is distributed in a single-atom state with a high probability, which confirms the successful synthesis of the catalyst.

[0053] Figure 3 The image shows the XRD pattern of Co-MPC. As can be seen from the image, no diffraction peaks of the crystalline cobalt phase were detected, further confirming that Co is in an atomically dispersed state in the sample.

[0054] Figure 4 The image shows the k²-weighted EXAFS (FT-k²-EXAFS) spectrum of Co-MPC. As can be seen from the figure, a main peak is observed at 1.40 Å in R-space, belonging to the first coordination layer of the Co-N scattering path. Almost no signal from the second coordination layer was observed, indicating that cobalt exists in single-atom form, consistent with XRD and HAADF-STEM observations.

[0055] Comparative Example 1

[0056] Step 1): Refer to Example 1.

[0057] Step 2): Do not proceed.

[0058] Step 3): Refer to Example 1, except that 0.4g of CoCl2·6H2O powder is used instead of 0.60g of Co-PZS powder.

[0059] The final electrode material is denoted as Co-MC@CF.

[0060] Comparative Example 2

[0061] Step 1): Do not proceed.

[0062] Step 2): Refer to Example 1.

[0063] Step 3): Refer to Example 1, except that Ti3C2Tx suspension is not added during the hydrothermal reaction.

[0064] The resulting electrode material is denoted as Co-PC@CF.

[0065] Comparative Example 3

[0066] Step 1): Refer to Example 1.

[0067] Step 2): Refer to Example 1, except that cobalt chloride hexahydrate (CoCl2·6H2O) is not added to prepare PZS powder.

[0068] Step 3): Referring to Example 1, replace Co-PZS powder with PZS powder.

[0069] The resulting electrode material is denoted as MPC@CF.

[0070] Example 2

[0071] In a dual-electrode system, 80 mL of uranium solution with an initial uranium concentration of 100 mg / L was taken and its pH was adjusted to 5. The effect of time on the electrochemical extraction of uranium using different electrodes prepared in Example 1 and Comparative Examples 1-3 was investigated. Figure 5 As shown, the Co-MPC@CF electrode has the highest uranium extraction capacity, with an extraction capacity of 4000 mg / g and a removal rate of 100% within 7 hours.

[0072] In a dual-electrode system, 80 mL of uranium solution with an initial uranium concentration of 100 mg / L was taken, its pH was adjusted to 5, and the reaction time was 420 min. The effect of voltage on the electrochemical extraction of uranium using the Co-MPC@CF electrode prepared in Example 1 was investigated. Figure 6 As shown, the Co-MPC@CF electrode exhibits the highest uranium extraction capacity when a square wave voltage of -5 to 0 V is selected. Therefore, subsequent experiments will use a voltage range of -5 to 0 V.

[0073] In a dual-electrode system, an 80 mL mixed solution containing U(VI), V(V), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ca(II), and Mg(II) was prepared, with all metal ions having a concentration of 10 mg / L. The pH of the solution was adjusted to 5, and the reaction was carried out for 420 min under a square wave voltage of -5 to 0 V. Water samples were then diluted, filtered, and the concentrations of each ion were measured using inductively coupled plasma mass spectrometry (ICP-MS). The selective adsorption capacity of the Co-MPC@CF electrode for different metal ions in the simulated water sample is shown in the figure. Figure 7 As shown, the Co-MPC@CF electrode exhibits good selectivity for uranium in solutions containing various interfering ions.

[0074] In a dual-electrode system, 80 mL of real seawater spiked with 100 mg / L U(VI) was used. The pH of the solution was adjusted to 5, and the reaction was carried out for 420 min under a square wave voltage of -5 to 0 V. After dilution and filtration, the absorbance was measured using a UV spectrophotometer, and the removal rate was calculated. The cycling stability of the Co-MPC@CF electrode was investigated using 1 M Na₂CO₃ solution as the electrode eluent. The results are as follows: Figure 8As shown, after six consecutive adsorption-desorption cycles, the electrode's uranium extraction capacity remains above 85%.

[0075] Example 3

[0076] Application study of Co-MPC@CF prepared in Example 1 in real seawater.

[0077] A real-world seawater electrochemical uranium extraction experiment was conducted on the single-atom Co-MPC@CF electrode prepared in Example 1. A simple electrochemical uranium extraction device was built under existing experimental conditions. A circulating pump continuously pumped 25 L of seawater into the electrochemical reaction cell. After uranium extraction was completed in the cell, the seawater was returned to the container at a constant flow rate, thereby maintaining a stable and dynamic processing procedure. Figure 9 The material exhibits excellent uranium extraction capabilities: the extraction capacity of uranium reached 40.50 mg / g within 14 days, with an average daily extraction of 2.89 mg / g / d. Notably, the electrode showed high initial activity in uranium extraction kinetics, with an extraction of 15.69 mg / g on the first day and a cumulative extraction of 24.31 mg / g in the first seven days (an average of 3.47 mg / g per day), demonstrating excellent potential for uranium extraction from seawater.

[0078] Example 4

[0079] Step 1): Refer to Example 1.

[0080] Step 2): Refer to Example 1.

[0081] Step 3): Refer to Example 1, the only difference being that the mass of the Co-PZS powder is adjusted to adjust the Ti3C2T content. x Ti3C2T in suspension x The electrodes prepared by mixing Co-MPC@CF-1, Co-MPC@CF-2, Co-MPC@CF-3, and Co-MPC@CF-4 with Co-PZS powder at mass ratios of 1:5, 2:15, 2:25, and 1:15, respectively, are respectively denoted as Co-MPC@CF-1, Co-MPC@CF-2, Co-MPC@CF-3, and Co-MPC@CF-4.

[0082] In a two-electrode system, 80 mL of uranium solution with an initial uranium concentration of 100 mg / L was taken, its pH was adjusted to 5, the reaction time was 420 min, and a square wave voltage of -5 to 0 V was applied to investigate the effects of Ti3C2T. x The effect of the ratio of suspension to Co-PZS powder on the electrochemical extraction of uranium by electrodes. Figure 10 As shown, Ti3C2T x Ti3C2T in suspension x Electrodes prepared with a mass ratio of Co-PZS powder controlled within 1:(5~15) all exhibit excellent electrochemical uranium extraction performance. In Example 1, the electrode prepared with Co-PZS powder in Ti3C2T...x Ti3C2T in suspension x The Co-MPC@CF electrode prepared by a mass ratio of 1:10 with Co-PZS powder exhibits the best performance.

[0083] Example 5

[0084] Step 1): Refer to Example 1.

[0085] Step 2): Refer to Example 1.

[0086] Step 3): Referring to Example 1, the only difference is that by adjusting the hydrothermal reaction temperature to 100℃, 110℃, 130℃, and 140℃, the prepared electrodes are respectively named Co-MPC@CF-5, Co-MPC@CF-6, Co-MPC@CF-7, and Co-MPC@CF-8.

[0087] In a dual-electrode system, 80 mL of uranium solution with an initial uranium concentration of 100 mg / L was taken, its pH was adjusted to 5, the reaction time was 420 min, and a square wave voltage of -5 to 0 V was applied to investigate the effect of hydrothermal reaction temperature on the electrochemical extraction of uranium. Figure 11 As shown, electrodes prepared when the hydrothermal temperature is controlled within 100~140℃ all exhibit excellent electrochemical uranium extraction performance. Among them, the Co-MPC@CF electrode prepared at 120℃ in Example 1 has the best performance.

[0088] In summary, this invention successfully constructed a three-dimensional binder-free composite electrode (Co-MPC@CF) by in-situ growing a cobalt single-atom-anchored polyphosphazene / MXene heterostructure on a carbon felt surface. This structure achieves uniform dispersion of the active components and full exposure of active sites. Under a square wave voltage of -5 to 0 V, the electrode achieves an ultra-high uranium extraction capacity of 4000 mg / g within 7 hours, while also exhibiting excellent selectivity and cycling stability, effectively overcoming the performance limitations of traditional electrodes due to the shielding of active sites. In natural seawater, this electrode also achieved a highly efficient uranium extraction capacity of 2.89 mg / g / d. This invention is expected to provide important support for the sustainable development of seawater uranium extraction and resource recovery.

[0089] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations, substitutions, modifications, equivalent improvements, or refinements that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, characterized in that: Includes the following steps: 1) Ti3AlC2 powder was etched in an HCl-LiF mixed solution and then ultrasonically exfoliated to obtain Ti3C2T x Nanosheet suspension; 2) After dissolving hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone and cobalt salt in a solvent, triethylamine was added, and a polycondensation reaction was carried out under ultrasonication to obtain Co-PZS; 3) Ti3C2T x After the nanosheet suspension is mixed evenly with Co-PZS and carbon fiber fabric, it is transferred to a hydrothermal reactor for hydrothermal reaction. The resulting hydrothermal reaction product is then dried and calcined to obtain a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms.

2. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1, characterized in that: The concentration of LiF in the HCl-LiF mixed solution is 60~100mg / mL, and the concentration of HCl is not less than 8mol / L; The ratio of Ti3AlC2 powder to the HCl-LiF mixed solution is measured according to a mass ratio of Ti3AlC2 to LiF of 1:(1.5~2.0).

3. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1 or 2, characterized in that: The etching conditions are: stirring reaction at 35~45℃ for 30~60h.

4. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1, characterized in that: The molar ratio of hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone and cobalt salt is (15~25):(5~15):

1.

5. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1, characterized in that: The conditions for the polycondensation reaction are: ultrasonic power of 150~210W, frequency of 35~45Hz, temperature of 25~50℃, and time of 0.5~2h.

6. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1, characterized in that: The Ti3C2T x The mass ratio of the nanosheet suspension to the Co-PZS is (5~15):1; The Ti3C2T x Ti3C2T in nanosheet suspension x The concentration of nanosheets is 3~7 mg / mL.

7. The method for preparing a polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 1, characterized in that: The hydrothermal reaction conditions are: reaction at 100~140℃ for 3~7 hours; The calcination conditions are as follows: calcination at 400~500℃ for 1~3 hours under a protective atmosphere.

8. A polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms, characterized in that: It is obtained by the preparation method described in any one of claims 1 to 7.

9. The application of the polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms as described in claim 8, characterized in that: It is used as the working electrode in a two-electrode system for the electrochemical adsorption of uranyl ions in solution.

10. The application of the polyphosphazene / MXene self-supporting electrode loaded with cobalt single atoms according to claim 9, characterized in that: During operation, the dual-electrode system operates at a voltage of -5 to 0V, a frequency of 300 to 500Hz, and a duty cycle of 40 to 60%.

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